This is a 3-year study designed to longitudinally investigate cognitive event-related potentials (ERPs) in a cohort of outpatient schizophrenic patients and their never mentally ill siblings. The focus will be on two aspects of the somatosensory (SEP) late positive component (P300 and Slow Wave), as well as the earlier SEP events beginning with peak N20 (negativity 20 msec poststimulus). The study groups include: (1) 40 outpatient RDC schizophrenics repeat tested four times at approximately six month intervals; (2) 40 never mentally will siblings repeat tested two times at approximately twelve month intervals; (3) 30 nonpatient controls, with ten or these controls being repeat tested two times at a twelve month interval. All schixophrenics will meet both DSM-III and SADS-L criteria for schizophrenia (chronic subtype), and may or may not have an Axis II personality disorder. In addition to diagnosis, all subjects will receive an intelligence test, personality inventory, and several ratings of symptom presence and severity (BPRS, Quality of Life Scale, Positive/Negative Symptom Scale). The major objectives are: (1) to determine whether cognitive ERP deviations in schizophrenia remain stable or covary with changes in clinical state across the course of illness; (2) to determine whether cognitive ERP deviations are present in "never mentally ill" siblings of schizophrenic patients; (3) to evaluate patterns of cognitive related changes in early SEP components from outpatient schizophrenics and their siblings. The findings from this study should help to determine the extent to which cognitive ERP deviations, in a cohort of schizophrenic patients and possibly their unaffected siblings, are the reflection of psychotic decompensation or a basic neurophysiologic defect that persists across clinical states, and is present in unaffected family members.